554 DOMESTIC ANIMALS, DAIRYING, ETC. 



be perfect and accurate. Threads should be true and cut to fit the 

 bur; rods should be of proper length and, if weights are used, they 

 should be so arranged that they can be fixed in the proper position. 

 The writer sees no use for the weight, nor does he favor a very long 

 lever. By principle of direct action the damper is its own weight, 

 and with the disk regulator no other weight seems necessary. In 

 some machines the regulator is cumbersome, takes too much space in 

 the egg chamber, and interferes with the handling of the trays; in 

 others it is loosely set and constantly getting out of balance and 

 dropping down upon the eggs or chicks. The disk regulator is less in 

 the way and less liable to fall down than any other that the writer 

 has used. 



Few machines are perfect in all their parts, but when one is 

 found that suits in most details it is kept and remodeled to suit every- 

 day requirements. Most manufacturers make a mistake in their fail- 

 ure to test every machine as a whole before sending it out. Made of 

 the same materials, from the same patterns, by the same machinery 

 and the same workmen, all mechanical products are liable to vary 

 somewhat in their action. Each incubator has an individuality, and 

 it requires a thorough test at the factory. The purchaser can feel 

 assured that plenty of incubators are now made by firms that test 

 them in the shops and whose regulators can be relied upon as surely 

 as can a watch or clock. So much has been written upon the subject 

 of ventilation that the reader need not expect the writer to add much 

 that is new to the literature upon this subject. One thing is sure, 

 namely, that in nature the mother hen is compelled to allow fresh 

 air access to her eggs. But she frequently makes her nest in places 

 where the air is far from good, and yet she gives us a fair hatch 

 regardless of atmospheric surroundings. It is not likely that fre- 

 quent currents of fresh air over the eggs are necessary to successful 

 incubation, nor does it seem certain that air in motion, even if it has 

 been warmed, is inclined to promote hatching. If the machine is 

 opened twice a day and the eggs taken out to be cooled or turned, 

 they get about all the ventilation they really need. But accidents 

 may happen ; there may be leaking of steam or smoke, or a breaking 

 of an overlooked decomposing egg, and, for fear that such an acci- 

 dent may happen between the hours of inspection, it is well to have 

 a system of moderate ventilation in operation. One of the best 

 methods is a circular hole in the bottom of the machine, this hole 

 being about 1% inches in diameter and covered with fine wire screen- 

 ing on the inside and provided with a slide of tin or other metal 

 upon the bottom or outside. This slide should be open when the 

 machine is first heated. It should work easily and be slightly open 

 all the time, and should be altered according to the weather. One 

 thing often overlooked is the quality of the air in the room occu- 

 pied by the incubator. The room should be clean, free from dust 

 and mold, moderately dry, and contain air of absolute purity. This 

 has more to do with the condition of the air in the egg chamber than 

 many are inclined to admit, and is, in the writer's opinion, the 

 major part of ventilation. 



